PROJECT SUMMARY/ABSTRACT The purpose of this Mentored Research Scientist Development Award (K01) is to help me become an independent investigator who conducts interdisciplinary, policy-relevant research on the individual, school, and community factors that put adolescents at risk for substance use and justice system contact. Specifically, I propose to investigate an issue previously unexplored: the role of substance use as a determinant and consequence of the ?school-to-prison pipeline??a set of policies and practices that make it more likely for some adolescents to become entrenched in the criminal justice system than to receive a quality education. The training from this K01 will allow me to (1) learn and apply more specialized, advance quantitative methods in complex nested data and causal inference for mediation and interaction; (2) gain expertise in racial and LGBTQ health disparities and (3) adolescent health and juvenile justice; and (4) gain skills in grant-writing, professional development, sampling methods, and data collection/acquisition necessary for submitting my first R01 proposal. My career development plan includes specific seminars, workshops, coursework, conferences, and tailored mentoring from a multidisciplinary team comprising experts in social/behavioral sciences, advanced quantitative methods, adolescent trajectories of substance use and mental illness, racial and LGBTQ disparities in health and school discipline, school policy and adolescent health, adolescent exposure to the criminal justice system, and criminological theory and juvenile justice. The proposed research is particularly important because school- based arrests have skyrocketed 300-500% since the 1990s, and out-of-school suspensions (which double the risk of arrest) have more than doubled over the past 40 years. However, there is a substantial gap in knowledge about the public health consequences of these trends, given that (1) adolescents with substance use problems have increased risk of exposure to the justice system, and exposure to the justice system increases subsequent risk of substance use problems; (2) substance use is a prototypical ?zero tolerance? infraction implicated in school discipline/arrest; and (3) there are known racial and sexual orientation disparities in school discipline and substance use. To fill this gap, the proposed research will (1) investigate prospective associations among substance use, teacher/school factors, school discipline, community factors, and school-based arrests with unprecedented multi-level, multi-source data on students, teachers, schools, and communities; (2) determine whether modifiable individual, teacher, school, and community factors explain racial and LGBTQ disparities in substance-use-related school discipline/arrests; and (3) test whether there is a reciprocal relationship between substance use, school discipline, and school-based arrests. This project will inform a NIDA R01 proposal that will expand and further develop K01 research findings. The new skills I acquire through this K01 will position me to become an independent researcher who integrates substance use, public health, and criminal justice research, and one of the few investigators studying the substance-use-related school-to-prison pipeline.